In the class Mammalia, the vertebral column or backbone presents only slight modifications, and everywhere shows the same characteristics as in man, who stands at the head of this division of the animal kingdom. The length of this column, however, varies much, and the number of vertebrae of which it is composed is far from being uniform. These numerical differences principally depend on the unequal development of the caudal portion, or tail-end, of the column. Thus, the tail-forming vertebrae sometimes do not exist at all,--amongst certain bats for example; in other instances we reckon forty, fifty, and even upwards of sixty of these bones. Among the greater number of mammals, the tail is of little use for locomotion, except that it acts in many cases as does the rudder of a ship, steadying the animal in his rapid movements, and enabling him to turn more easily and quickly. Among some animals, it becomes a very powerful instrument of progression. Thus, in the kangaroos and jerboas, the tail forms, with the hind feet, a kind of tripod from which the animal makes its spring. With most of the American monkeys it is prehensile, and serves the animal as a fifth hand to suspend itself from the branches of trees; and, lastly, among the whales, it grows to an enormous size, and becomes the principal instrument for swimming.
Reading list for 2012!
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Believe it or not but I have been reading books in 2011. Mostly on my
Kindle, but I did forget to update this blog. However I thought it would be
good to r...
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